This research involves the study of the diffuse reflectance of esthetic dental materials (i.e., porcelain and composite restorative materials). Mathematical models will be derived and evaluated for application to these optically non-homogeneous materials. At present, the development of new materials with superior mechanical and wear properties is hindered by a lack of understanding of the complex optical phenomena that underlies the natural appearance of these materials. The effects of absorption, specular reflectance and scattering will be predicted by the mathematical model and compared with experimental data. In addition, experiments on the sensitivity of observers to detect apparent translucency differences will be assessed. The general and basic nature of this research will give a solid basis for the understanding of the simulation of translucency by widely used clinical restorative materials.